The purpose of this study was to investigate the enhancement of heat transfer without additional external power in the case of rectangular impingement air jet vertically on the flat heating surface. The technique used in the present study was placement of square rod bundles as a turbulence promoter in front of the heat transfer surface. The results obtained through this study were summerized as follws. High heat transfer enhancement was achieved by inserting rods in front of the heating flat plate. According to visulaization, it was examined because of flow acceleration and separation and disturbance of boundary layer. The smaller clerance between rod and heating plate was, the larger heat transfer effect became at each H/B. Arverage Nusselt number reached maximum at H/B=10 and the local augmentation rate of heat transfer became maximum at H/B=2. The maximum average heat transfer enhancement rate increase about 43% for the case of X/B=2 and C=1mm, compared to a flat plate without rods. The correlating equation of average Nusselt number and Reynolds number was obatined. As follws : ${overline{Nu}}_0=1.249Re^{0.465}(C/A)^{-0.033}(H/B)^{0.013}$.